Blanket bar for narrow gap cylinders

ABSTRACT

A blanket bar assembly for use on a printing blanket comprising a U-shaped bar having a centrally located channel and two arms extending outwardly from the channel in a substantially parallel relationship. Inwardly directed projections are provided on one or both arms and are directly aligned with holes on the opposite arm or arms. The projections are of such a length so as to be capable of extending through the holes and be deformed so as to lock the arms together. A printing blanket edge inserted into the channel and pierced by the projections is thereby securely fastened to the blanket bar.

This invention relates to a blanket bar for securely attaching aprinting blanket to a printing press, and more particularly, thisinvention relates to a blanket bar for mounting and securing blankets onpresses wherein the blanket cylinder has a gap width less than 0.250inches.

BACKGROUND

Printing blankets are generally made of one or more layers of cloth andother materials and generally have at least one surface coated with arubber or other elastomeric material which acts as a transfer surface totake the ink image from the printing plate and transfer it to the paperon which it is to be printed.

Conventionally, these printing blankets are mounted onto the outercircumferential surface of a printing cylinder and are secured in placeby various attachment means, such as reel rods or clamps. See forexample, U.S. Pat. Nos. 4,261,262 and 3,675,573.

In order to ensure a secure attachment, the leading and trailing edgesof the blankets are reinforced with a rigid bar, known in the industryas a blanket bar.

Blanket bars are generally made of metal, such as strip steel orextruded aluminum and are held in place by screws, bolts, rivets and/oradhesives.

One type of blanket bar has a "V" or "U" shaped channel with twoextending arms which surround the edge of the blanket. For example, U.S.Pat. No. 3,675,573 shows a "V" shaped bar of extruded aluminum with eacharm having an inwardly directed ridge so that when the arms arecompressed into contact with the blanket edge, the ridges grip theblanket edge and hold the bar in place.

Another example is shown in U.S. Pat. No. 3,883,940 in which a series ofprongs are formed in one arm of the bar. When crimped in place, theteeth bite into the blanket to fasten the bar to the blanket.

All of the bars discussed above suffer from serious drawbacks. Forexample, adhered bars are difficult to work with, labor intensive,cumbersome, expensive and frequently fail. When there is an adhesivefailure, there is immediate separation of the blanket from its retainingdevice and the results are often catastrophic and can include damage tothe printing press. Likewise, riveted bars and ridged bars, as discussedabove, cause the blanket to pucker which increases the blanket thicknessand tends to weaken the blanket in that area. Further, bars with teeth,as discussed above, are often subject to failure as these bars tend toopen up, allowing the blanket to slip out of the bar and retainingmeans.

These problems have become even more severe in newer presses where thegap in the blanket cylinder has become narrower.

The newer presses have blanket cylinders where the gap, through whichthe ends of blanket are inserted and retained, has been narrowed fromabout 0.250 inches to less than 0.210 inches and more preferably lessthan 0.190 inches. Narrowing the gap reduces the incidence of cylinder"bounce" during printing. Bounce is a vibration caused by the impact ofthe edges of the gap against an adjacent printing roll. Bounce adverselyaffects (1) printing quality, causing streaks and runs and (2) machinewear, causing a rapid increase in the rate of wear of the bearings,bearers, cylinders, etc. and (3) may also reduce blanket life. Thenarrow gap also increases the number of printable lines on a cylinder ofgiven size and reduces paper trim losses. Because of these benefits andthe development of pinless folders among other factors, presses equippedwith blanket cylinders having narrower gaps have become increasinglymore popular. These newer presses are sometimes referred to as narrowgap presses.

Narrow gap presses require thinner blankets and thinner bars. Extrudedaluminum bars cannot be made thin enough to be used on a narrow gappress and still provide the required rigidity and retention strength.Likewise, riveted bars, because they pucker the blanket and increase theblanket thickness, are not acceptable. The "U" shaped bar as disclosedin U.S. Pat. No. 3,883,940 is impractical in a thin design because thereis not sufficient strength in the bar to prevent it from opening up andallowing the blanket to slip out of the bar and retaining means. Theproblems with adhered bars become magnified in narrow gap presses.

The present invention while preferably used on narrow gap presses, canbe used on other presses as well, and provides a simple, efficient meansfor ensuring the retention of the bar to the blanket.

SUMMARY

It is an object of the present invention to provide an inexpensive,thin, rigid blanket bar for use on printing blankets, especially onprinting blankets used on newer presses equipped with blanket cylinderswhich have a narrow gap, i.e. less than 0.210 inches.

It is a further object of this invention to provide a blanket barcomprising an elongated strip of metallic material having a U-shapedchannel and a first and second arm extending outwardly from the channelin parallel relationship to each other, at least the first arm havingone or more projections extending outwardly from the first arm towardthe second arm, at least the second arm having one or more holes throughwhich the projections are capable of extending and being clenched overto lock the first and second arms together.

Another object is to provide a blanket bar having a series of lockingprojections having a triangular, rectangular or circular shape.

It is an object of the present invention to provide a printing blanketand blanket bar assembly for use in a printing press comprising aprinting blanket having a leading and trailing edge, blanket barssecured to the leading and trailing edges, wherein each blanket bar hasa channel and a first and second arm extending outwardly from thechannel, the first and second arm being in a parallel relationship toeach other, the printing blanket being between the first and second armsand abutting an inner surface of the channel, the first and second armshaving a series of projections and holes, the projections of the firstarm being in alignment with the holes of the second arm and theprojections of the second arm being in alignment with the holes of thefirst arm, the projections of the first and second arms extendingthrough the printing blanket and the holes in the other arm and beingbent over onto the outer surface of the first and second arms so as tosecure each blanket bar to the edges of the printing blanket.

It is another object to provide a blanket bar and printing blanketassembly wherein the thickness of the assembly is no greater than thesum of the blanket thickness plus the thickness of each arm of the barand more preferably, the total thickness of the assembly is at least0.002 inches less than the sum of the blanket thickness plus thethickness of each arm of the bar.

The present invention provides a simple and economical blanket bar being"U" shaped and having a channel and two radial arms extending outwardlyfrom the channel. Inwardly directed projections on one or both arms areprovided and holes are provided on one or both arms directly oppositeand in alignment with the projections on the opposite arm, theprojections are of a length sufficient to extend through thecorresponding holes on the other arm and to be deformed over so as tolock the two arms together. A printing blanket inserted into the channeland pierced by the projections can therefore be securely fastened to thebar.

These and other objects of the present invention will be readilyapparent from the embodiments thereof presented in the followingspecification, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show preferred embodiments of the presentinvention, in which

FIG. 1 is a cross-sectional view of the blanket bar;

FIG. 2 is a cross-sectional view of the blanket bar and printing blanketas assembled for use;

FIGS. 3-7 are cross-sectional views of other preferred embodiments ofthe projections.

DETAILED DESCRIPTION

In FIG. 1 is a preferred embodiment of the present invention.

The blanket bar 1 is generally formed in a U or V shape, having achannel portion 2 and two outwardly extending arms 3a and 3b which aresubstantially parallel to each other. On arm 3a is a projection 4. Anopening 5 is optionally formed when the projection 4 is made in the arm3a. The opening can occur when the projection is punched, stamped orotherwise formed out of the substantial flat surface of the arm 3a.

On arm 3b is a hole 6 substantially in alignment with the projection 4of arm 3a. The hole 6 may be formed in any well known manner such aspunching, stamping, drilling or casting.

FIG. 2 shows the blanket bar attached to a printing blanket edge 7. Theblanket edge 7 is inserted between the arms 3a and b and butted upagainst the inner surface of the channel 2. The arms 3a and 3b have beenmoved toward each other so as to engage the surface of the blanket. Theprojection 4 has pierced through the blanket and extends through thecorresponding hole 6 to a point beyond the outer surface of arm 3b. Theoutermost tip 8 of the projection 4 has been deformed so as to lock thetwo arms together and thereby securely fasten the blanket bar to theblanket edge.

It is understood that the blanket bar is preferably of a lengthcorresponding to the length of the blanket edge. The width of the arms3a and b is not critical to the invention. The width should besufficiently wide to ensure that the blanket bar is properly attached tothe blanket edge and that the resultant assembly is sufficiently rigidso as to resist deformation when the typical tensions are applied duringuse in the press. Likewise, the width should not be so long as tointerfere with the attachment mechanism, such as a reel rod or as tomake the assembly unduly expensive or cumbersome. Furthermore, there isno requirement that arms 3a and 3b be the same width, so long as thecorresponding projections and holes are in alignment.

The channel, 2, is preferably centralized although it may not be in acentral location when the arms are of different widths. In all cases,the channel should be formed sufficiently toward the center of the barso as to ensure adequate length to the arms and retention of the bar tothe blanket. The channel may be of a simple design as shown in FIG. 1 ormay be more complex as depicted in FIGS. 5 and 6. The exact shape may befurther optimized to achieve maximum stiffness and minimize anydistortion which might occur while the blanket is mounted on the press.

The projections are preferably triangular in shape, though they can berectangular as shown in FIG. 4 or circular as shown in FIG. 7 or anyother shape which is capable of extending through a hole on the oppositearm and is capable of being deformed to lock the bar in place.

The holes may also be of similar shapes to those of the projections,though preferably the holes are rectangular in shape.

The projections and holes may be on one or both arms, as shown by FIG.3. They may be formed in rows as in FIG. 4 or alternating rows and maybe spaced at regular or irregular intervals. The arrangement is notcritical so long as the projections align with holes on the opposite armand securely fasten the bar to the blanket.

The projections and holes may be made in any manner conventional tometalworking. Examples of such include but are not limited to stamping,punching, drilling and casting. Preferably, the projections and holesare formed simultaneously by a die punch on a flat sheet of metal, suchas strip steel which is then bent to form the channel and arms. Theprojections and holes can be formed when the metal is cast and thenformed into the required shape, though such a process would be moreexpensive and time consuming.

In addition to the projections and holes, other embossments, such asridges, points, teeth, etc. may be added to one or both arms to enhanceadhesion of the bar to the blanket. These embossments do not have topenetrate the entire blanket thickness and preferably do not.

It may also be desirable to use an adhesive in addition to theprojections and holes. Suitable adhesives for the present inventioninclude self-curing two component epoxies, heat set phenolic nitrileadhesives and hot melt adhesives, all commonly used in the printingindustry and commercially available.

Materials useful in the present invention for the blanket bars includebut are not limited to the various grades of stainless steel, stripsteels which preferably have a corrosion resistant coating such aspaint, lacquer and other rust proof finishes, and various sheet metals.The material selected should be sufficiently strong to resist kinkingand excess bending, but should be sufficiently ductile to allow for theformation of the channel, arms, projections, holes and other retentionaids formed on or in the material. Preferably, stainless steel is usedbecause of its strength, ductibility and corrosion resistance. Thematerial selected has a thickness of from about 0.005 to about 0.020inches, preferably from about 0.010 to about 0.020 inches.

It is desirable that the thickness of the blanket and bar assembly be asthin as possible. While the assembly may be thicker than the sum of thethicknesses of the blanket and metal in each arm of the bar, it is apreferred embodiment of this invention that the thickness of the blanketand bar assembly be no greater than the sum of the blanket thicknessplus the thickness of the metal in each arm of the bar. In the mostpreferred embodiment, the final thickness of the blanket and barassembly is at least 0.002 inches less than the sum of the blanketthickness plus the thickness of the metal in each arm of the bar.

A preferred example of the present invention as shown in FIGS. 1 and 2is formed from a flat piece of stainless steel, having a total width of1.5 inches and a thickness of 0.015 inches. Approximately 0.25 inches infrom the longitudinal edge of the piece, a series of rectangular holes,0.125 of an inches wide and 0.186 inches long, are formed by punchingwith a die punch. The holes are spaced 0.5 inches apart, measured fromcenter to center. A corresponding series of triangular projections areformed by a die punch, approximately 0.25 inches in from the otherlongitudinal edge. The base of the projection is closest to thelongitudinal edge and measured 0.25 inches in width. The height of theprojection was 0.186 inches and the projections were spaced 0.5 inchesapart, as measured from center to center of the base. The projectionsand holes were in parallel alignment. The strip was then bent at itsmiddle to form a channel and two arms each approximately 0.75 incheslong. The projections of one arm faced inwardly toward the other arm andthe projections and holes were aligned with each other. A thin blanket,POLYWEB® by W. R. Grace & Co., having a thickness of 0.067 inches wasinserted into the channel and butted up against the inner end of thechannel. The arm having the projections was moved toward the other armin a clamping device, such as a break press (hydraulic or air activated)until the projections had pierced through the blanket and holes andextended about 0.109 inches beyond the outer surface of the armcontaining the holes. The projections were then deformed by bending orclenching over in a direction away from the channel so as to liesubstantially flat against the outer surface of the arm containing theholes. It was found that the projections in being clenched over slightlydeformed the edge of the holes through which they extended so that theprojections were substantially flush with the outer surface of the arm.The thickness of the blanket and bar assembly was approximately 0.095inches as measured from outside to outside surface. The assemblythickness was about 0.002 inches less than the sum (0.097) of theblanket thickness (0.067) and the thickness of the metal in each arm(0.015×2=0.030), resulting in a blanket and bar assembly which isthinner than other assemblies and as strong, if not stronger than otherassemblies.

The projections which penetrate the other arm are clinched to preventthe arms from opening or spreading apart, thereby maintaining itscrimped dimension. Failure to maintain the initial crimped thicknesswould make blanket removal from the cylinder more difficult.

Thin metals, i.e. those less than 0.015 inches, do not have sufficientstrength to maintain proper caliper at the extreme edge of the arms,even if they are adhesively bonded to the blanket. Through the use ofthe present invention namely, the introduction of appropriateprojections in at least one arm and corresponding recesses in the otherand the engagement and clenching of those projections, a mechanicalmeans is provided for maintaining the preferred thickness of the barredblanket at the extreme edges of the arms of the bar, even with thinmetals.

The present invention represents an important improvement in theprinting industry, eliminating one of the problems which has preventedthe large scale acceptance and use of narrow gap cylinders and theirassociated blankets and bars.

While this invention has been described with reference to its preferredembodiments, other embodiments can achieve the same result. Variationsand modifications of the present invention will be obvious to thoseskilled in the art and it is intended to cover in the appended claimsall such modifications and equivalents as fall within the true spiritand scope of this invention.

What I claim is:
 1. A blanket bar comprising an elongated strip of metalhaving a channel, first arm and second arm radiating outwardly from thechannel in parallel relationship to each other, the first arm and secondarm having a series of projections perpendicular to the plane of thefirst and second arms, the first and second arms having a series ofholes in alignment with the series of projections on the other arm, theprojections being of such length as to extend through the holes on theother arm and capable of being clenched over so as to lock the first andsecond arms together.
 2. A blanket bar of claim 1 wherein the metal isselected from the group consisting of stainless steel and corrosionresistant strip steel.
 3. A blanket bar of claim 1 wherein the thicknessof the metal is from about 0.005 to about 0.020 inches.
 4. A printingblanket and blanket bar assembly comprising a printing blanket having aleading edge and a trailing edge, a first and second blanket barfastened to the leading and the trailing edge, the first and secondblanket bars being U-shaped and having a first and second arm projectingoutwardly in a substantially parallel relationship to each other from acenter of the bar, the first and second arms having a series ofprojections and holes arranged so that the projections of one arm are inalignment with the holes of another arm; the projections of the firstand second arms extending through the blanket and the correspondingholes in the other arm and being deformed over so as to lock the blanketbars to the edges of the blanket.
 5. The assembly of claim 4 wherein theprojections are deformed by being clenched over.
 6. The assembly ofclaim 4 wherein the bar is selected from the group consisting ofstainless steel and corrosion resistant strip steel.
 7. The assembly ofclaim 4 wherein the thickness of the blanket and bar assembly is equalto or less than a sum of a blanket thickness plus thickness of the armsof the bar.
 8. The assembly of claim 7 wherein the thickness of blanketand bar assembly is at least 0.002 inches less than the sum of theblanket thickness plus the thickness of the arms of the bar.
 9. Theassembly of claim 4 wherein the projections are triangular in shape andthe holes are rectangular in shape.
 10. The assembly of claim 4 whereinthe projections are tubular in shape and the holes are circular inshape.
 11. The assembly of claim 4 wherein the projections and holes arerectangular in shape.
 12. The assembly of claim 6 wherein the bar has athickness of from about 0.005 to about 0.020 inches.
 13. A printingblanket and blanket bar assembly comprising a printing blanket having aleading edge and a trailing edge, a first blanket bar fastened to theleading edge of the blanket and a second blanket bar fastened to thetrailing edge of the blanket, the first and second blanket bars beingformed of a metallic material having a thickness of from about 0.005 toabout 0.020 inches, the metallic material being U-shaped and having afirst and second arm projecting outwardly in a substantially parallelrelationship to each other, the first and second arms having a series ofprojections and holes arranged so that the projections of one arm are inalignment within the holes of another arm; the projections of the firstand second arms extending through the blanket and corresponding holes inthe other arm and being deformed so as to lock the first and secondblanket bars to the leading and trailing edges of the blanket; and theprinting blanket and blanket bar assembly have a thickness equal to orless than a sum of the blanket thickness plus a sum of thickness of thearms of the bar.
 14. The assembly of claim 13 wherein the thickness ofthe blanket and bar assembly is at least 0.002 inches less than the sumof the blanket thickness plus the thickness of the arms of the blanketbar.